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HHMI's Holiday Lectures on Science

Howard Hughes Medical Institute

The Howard Hughes Medical Institute is a philanthropy that supports biomedical research and science education. As part of its mission to strengthen science education, the Institute presents the Holiday Lectures on Science, an annual series that brings the latest developments in a rapidly moving field of research into the classroom.

Archived from iTunes at https://itunes.apple.com/us/podcast/hhmis-holiday-lectures-on-science/id214106297. Items in this collection are restricted.

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HHMI's Holiday Lectures on Science
Jun 15, 2017 HHMI/Mary E. Power, PhD
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Many rivers of the world have vast seasonal changes in flow rates. Dr. Mary Power leads us in an exploration of Northern California’s Eel River and how the community of herbivores and predators is affected by changes in river flow. Drought years with no winter floods generate a very different ecosystem compared to years with floods. Human-induced water shortage will also have a drastic detrimental effect on river ecology.
HHMI's Holiday Lectures on Science
Jun 15, 2017 HHMI/Brian R. Silliman, PhD
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Coastal wetlands are dominated by a variety of plants adapted to a stressful environment. In the absence of a significant number of herbivores, the growth of these plants was thought to be limited only by nutrient availability. Through experiments, Dr. Brian Silliman revealed that salt marshes, like many other terrestrial ecosystems, are mainly controlled by the top-down forces of herbivores and other consumers.
HHMI's Holiday Lectures on Science
Jun 15, 2017 HHMI/Brian R. Silliman, PhD
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Many rivers of the world have vast seasonal changes in flow rates. Dr. Mary Power leads us in an exploration of Northern California’s Eel River and how the community of herbivores and predators is affected by changes in river flow. Drought years with no winter floods generate a very different ecosystem compared to years with floods. Human-induced water shortage will also have a drastic detrimental effect on river ecology.
HHMI's Holiday Lectures on Science
Jun 15, 2017 HHMI/Mary E. Power, PhD
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The ecosystem of a river depends on complex interactions between primary producers, grazers, and predators, which in turn are determined both by the traits of the individual species involved and the physical conditions of the river. River ecologist Dr. Mary Power illustrates these principles by describing how the dominant grazing fishes in a river ecosystem play a critical role in forming the aquascape.
HHMI's Holiday Lectures on Science
Jun 15, 2017 Howard Hughes Medical Institute
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A discussion of the Chesapeake Bay Watershed, its complex food web, and the challenges of conserving and restoring the bay. Followed by a general discussion on ecology with the lecturers and students attending the 2016 Holiday Lectures, moderated by HHMI vice president of Science Education, Dr. Sean Carroll.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Corina E. Tarnita, PhD
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Regular spatial patterns abound in natural systems. Understanding how patterns arise in ecosystems provides insights into how these ecosystems function.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Corina E. Tarnita, PhD
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Gorongosa National Park in Mozambique provides several examples for how to model the growth of animal populations and then check the models against actual data.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Robert M. Pringle, PhD and Corina E. Tarnita, PhD
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Ecosystems include complex interactions between animals and plants, which can be measured experimentally and investigated using mathematical models.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Alexandra Swanson, PhD and Roland Kays, PhD
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A discussion of camera traps and their use in ecological research.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI
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The 2015 Holiday Lecture discussion session.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Robert M. Pringle, PhD
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Two important questions in ecology are "How do we conserve ecosystems?" and "When we try to restore damaged ecosystems, what state do we restore them to?"
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Robert M. Pringle, PhD
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Savannas cover 20 percent of Earth’s surface and much of Africa. The patterns and processes that occur in this globally important biome illustrate core concepts in ecology.
HHMI's Holiday Lectures on Science
Mar 10, 2016 HHMI/Robert M. Pringle, PhD
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Large herbivores in the African savanna coexist by partitioning ecological niches by time, space, and diet.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Anthony D. Barnosky PhD
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The fossil record contains evidence of five mass extinctions, when more than 75 percent of species went extinct. Mammals are a key group for comparing past and present extinction rates. Many living species are threatened, but there is still time to avoid a sixth mass extinction.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Anthony D. Barnosky PhD, Elizabeth A. Hadly PhD, Stephen R. Palumbi PhD
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A sixty minute discussion on biodiversity with the lecturers and students attending the 2014 Holiday Lectures. Moderated by HHMI vice president of Science Education, Dr. Sean Carroll.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Stephen R. Palumbi PhD
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Ocean biodiversity is also threatened by human activities. But because the ocean is huge and has highly diverse environments, marine organisms appear to be more resilient than land animals when threatened by extinction and can bounce back with modest conservation efforts.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Elizabeth A. Hadly PhD
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Human activities have caused the extinctions of many species in the past, and that is also happening today. Human population growth is driving habitat destruction and climate change, both direct threats to biodiversity.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Anthony D. Barnosky PhD
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The current threats to biodiversity are tightly coupled to human demand for power, food, and money. We can avoid a sixth mass extinction by rethinking how we use energy, how we feed the world, and the value we place on intact ecosystems.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/by Elizabeth A. Hadly PhD
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The loss of biodiversity also means a loss of genetic diversity, which is the biological toolkit for adaptation. As populations of animals become increasingly isolated due to habitat fragmentation, assisted migration may be a strategy for preserving genetic diversity.
HHMI's Holiday Lectures on Science
Mar 16, 2015 HHMI/Stephen R. Palumbi PhD
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Coral reefs are threatened by many human activities, including global ocean warming from climate change. Some corals can survive unusually high temperatures by virtue of their genetic makeup. These heat-tolerant corals may hold the key to preserving coral reefs into the future.
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Elinor Karlsson, PhD
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Dr. Elinor Karlsson of the Broad Institute discusses using dogs in genome-wide association studies (GWAS), and the genetic evidence for dog domestication, as revealed by copy-number variations in the amylase gene.
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Charles Sawyers, MD and Christopher Walsh, MD PhD
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Dr. Charles Sawyers and Dr. Christopher Walsh discuss wide-ranging topics with students, including autism, cancer, and scientific career choices.
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Charles Sawyers, MD
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Despite decades of research, cancer continues to be a major cause of death in the United States. The disease is traditionally treated by a combination of surgery, radiation, and chemotherapy, which can have severe side effects. Recent advances in cancer biology have led to the development of targeted drugs as new and effective treatment options for some types of cancer. Dr. Charles Sawyers presents an overview of cancer biology and describes how understanding the molecular mechanisms involved...
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Christopher Walsh, MD PhD
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The human brain is a complex network of cells whose organization and function are controlled by many genes. By working with patients who have developmental brain disorders, Dr. Christopher Walsh and his team have begun to identify genes that are required for proper brain development. This research has led to some surprising insights, such as a connection between cell division orientation and cell fate during the development of the cerebral cortex.
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Charles Sawyers, MD
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Based on early successes with targeted drug therapy, the cancer research community prioritized sequencing the genomes of thousands of tumor samples to identify every gene mutated in cancer. Approximately 140 such genes have been identified to date. They can be classified into three main functional groups according to their roles in normal cell biology: genes that affect cell growth and survival, cell fate, and genome maintenance. Cancers can now be classified not only by the type of tissue and...
HHMI's Holiday Lectures on Science
Apr 7, 2014 HHMI/Christopher Walsh, MD PhD
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Autism is a general term for a spectrum of disorders of brain development that range in severity from mild to severe. Because autism is not a single disease, it has been difficult to identify its causes. Dr. Christopher Walsh describes how recent advances in DNA sequencing technology have made it possible to study large cohorts of patients and find genes that are most commonly disrupted in children with autism. These studies show that all currently known genes associated with autism are also...
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Andrew Knoll, PhD
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The fossil record contains evidence of large animals only for the most recent 15 percent of Earth's history. Before then, life on our planet consisted primarily of microbes, which have left microfossil and chemical evidence of their existence. Microbes had a profound effect in shaping Earth's environment in the past. For example, when cyanobacteria evolved oxygen-generating photosynthesis, the event led to the oxygenation of the atmosphere and the evolution of eukaryotes and animals. Today many...
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Naomi Oreskes, PhD
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Accepting a scientific theory as scientific knowledge requires broad consensus among scientists. The theory of continental drift, which eventually became known as the theory of plate tectonics, was a remarkable synthesis of different lines of evidence. Yet, when first proposed in the 1920s by Alfred Wegener, the theory was rejected by many scientists. The story of how the theory eventually became accepted, many decades later, provides a fascinating glimpse into the process of building new...
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Andrew Knoll, PhD, Daniel Schrag, PhD and Sean Carroll, PhD
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The lecturers Andrew Knoll and Daniel Schrag discuss topics relating to climate change as they answer questions from students in the audience. Moderated by HHMI investigator and VP of Science Education, Sean Carroll.
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Daniel Schrag, PhD
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Changes in the atmospheric concentrations of greenhouse gases, such as carbon dioxide (CO2), influence Earth’s temperature. Geologic records show that Earth has been both much cooler and much warmer in the past compared to today, but this change in temperature was driven by a gradual rate of change in atmospheric CO2 concentrations. The rate of modern day increases in CO2 is unprecedented in human history and will have serious consequences in the near future and beyond, in terms of climate...
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Andrew Knoll, PhD, Sean Carroll, PhD, Kirk Johnson, PhD, Tyler Lyson, PhD
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Students engage in a lively discussion about the film with Andrew Knoll of Harvard University; Sean Carroll, executive producer of the film; and two researchers featured in the film: Kirk Johnson, director of the National Museum of Natural History; and Tyler Lyson, postdoctoral researcher at the National Museum of Natural History.
HHMI's Holiday Lectures on Science
Apr 29, 2013 HHMI/Naomi Oreskes, PhD
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There is strong consensus among climate researchers that, based on careful analysis of the scientific evidence, human activities are causing climate change. Yet, the American public remains highly skeptical of this conclusion. Why? A look at this country’s history provides the answer. A Cold-War era think tank became an influential source of anti-regulation sentiment, swaying public opinion on many issues, from the harms of cigarette smoke to acid rain, and now, climate change.
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI/Sarah Tishkoff, PhD and Michael Campbell, PhD
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Dr. Michael Campbell discusses how humans perceive the test of the chemical PTC. With Dr. Sarah Tishkoff, he fields questions about the evolution of taste perception, and scientific career choices.
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI/Tim White, PhD
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In 1994, scientists discovered the remarkably well-preserved fossil of "Ardi," a member of the 4.4-million-year-old species Ardipithecus ramidus. Fossils found with Ardi indicate that she lived in a woodland rather than savanna habitat. Even more surprising than her ecology is the unique combination of humanlike and chimplike anatomical features. Ardi’s remains illuminate the divergent evolutionary histories of living chimpanzees and humans.
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI
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The lecturers and science reporters Ann Gibbons and Charles Petit discuss the particular challenges that arise when communicating scientific findings to the public.
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI/John Shea, PhD
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Archaeology is the study of human residues using the scientific method to reconstruct human behavior. Residues are anything that results from human action, including stone tools. Tools are important in differentiating humans from other animals, and stone tools can be preserved over millions of years. By studying stone tools, scientists have learned how past human species might have lived and behaved, and how early humans differed from chimpanzees.
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI/Sarah Tishkoff, PhD
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The analysis of DNA sequences reveals the genetic heritage of modern humans. Using genetic evidence, scientists established that modern humans (Homo sapiens) originated from Africa. As groups of modern humans dispersed from Africa, they adapted to different environments around the globe. Genetic variations in human populations account for these adaptations, which continue to play a role in our lives. Examples of adaptations include what we choose to eat, what we are able to digest, and how...
HHMI's Holiday Lectures on Science
Apr 9, 2012 HHMI/Tim White, PhD
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One of the most profound questions we can ask is "Where have we come from?" Charles Darwin addressed this question in his book on human evolution, The Descent of Man, which was published in 1871. Since then, scientists have gathered fossil and genetic evidence to give shape to the human evolutionary tree. Evolutionary science, like all science, involves processes for building a body of knowledge based on reason and evidence, and requires both creativity and critical thinking.
HHMI's Holiday Lectures on Science
Mar 1, 2011 HHMI/Eva Harris, PhD
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The Virochip has been used to identify the infectious agents of SARS and other diseases. When the Virochip alone is not enough, new DNA sequencing technologies have been used to sequence all the nucleotides in the sample. Bioinformatic tools can then identify those sequences that are of viral origin. Recent advances in sequencing technology suggest that personal genome sequencing could become routine in the not too distant future.
HHMI's Holiday Lectures on Science
Mar 1, 2011 HHMI/Eva Harris, PhD
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Dengue virus comes in four subtypes. Fighting off a first dengue infection increases the risk for developing a more severe form of dengue fever if they are infected a second time with a different dengue virus subtype. Dengue virus leverages the immune system to its advantage. Enhancing developing countries’ scientific and clinical infrastructure can help the international effort to counter the spread of dengue.
HHMI's Holiday Lectures on Science
Mar 1, 2011 HHMI/Laura D. Kramer, PhD, Robin M. Moudy, PhD
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Mosquitoes are vectors for many viral diseases including dengue fever and West Nile. Understanding how a virus infects the mosquito is important in understanding how the disease will spread. On Grand Cayman, transgenic mosquitoes have been used in an effort to eradicate the mosquito vector. This discussion explores the ethics of genetically-modified organisms and other topics.
HHMI's Holiday Lectures on Science
Mar 1, 2011 HHMI/Joe DeRisi, PhD
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The first step in the battle against any infectious disease is to identify the infectious agent. Viruses can be identified based on their proteins or their genome. The Virochip is a DNA microarray diagnostic tool that can detect the genomes of known viruses as well as previously unknown varieties of viruses. Virochip technology is based on the basic molecular biology of DNA and RNA hybridization.
HHMI's Holiday Lectures on Science
Mar 1, 2011 HHMI/Eva Harris, PhD
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Dengue fever is a rapidly re-emerging disease that has been spreading throughout Central America and is now being detected in the U.S. It is particularly devastating in tropical countries where healthcare resources are stretched thin. Dengue virus is spread by mosquitoes, and community-based efforts to control breeding mosquitoes have been effective.
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Bonnie L. Bassler, PhD
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Dr. Bonnie Bassler discusses antibiotics development, quorum sensing, and other topics related to bacteria in a question-and-answer session with a student audience.
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Bonnie L. Bassler, PhD
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Pathogenic bacteria use quorum sensing to launch a simultaneous attack when in sufficient numbers. Bacteria possess at least two systems of quorum sensing. They sense their own species' numbers by monitoring their species-specific quorum sensing signal. Bacteria also sense a signal that is shared between different species to obtain information about the bacterial community. Manipulating quorum sensing is a promising approach for developing new antibiotics against pathogens, or probiotics for...
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Baldomero M. Olivera, PhD
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Cone snail venoms have a wide variety of effects, ranging from convulsive shock, to paralysis, to sedation. The venoms contain a mixture of peptide toxins that simultaneously attack different molecular targets of the nervous system. The evolution of such a diversity of toxins is made possible by multiple gene superfamilies containing hypervariable sequences. The research and medical value of a group of animals like the cone snails is a powerful reminder of what we can learn from biodiversity....
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Baldomero M. Olivera, PhD
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Dr. Baldomero Olivera discusses various aspects of the biology of the venomous cone snails in a question-and-answer session with a student audience.
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Bonnie L. Bassler, PhD
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Bacteria live in and on us in complex communities that outnumber the cells and genes of our own tissues. These bacteria possess a communication mechanism that allows them to coordinate their activities. This mechanism, called quorum sensing, was first described in bacteria living symbiotically in a squid. The bacteria produce bioluminescence which simulates moonlight and camouflages the squid. The key to quorum sensing is a molecular signal released by the bacteria that is monitored by...
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/Baldomero M. Olivera, PhD
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Natural selection has produced an astounding array of venoms for prey capture. Marine cone snails are among the most dangerous venomous creatures. Cone snail venoms are potent, deadly to fish and people, and each species makes a venomous cocktail of up to 200 different toxins. One of these toxins has been developed into a drug called Prialt–a pain killer that prevents the spinal cord from relaying pain information to the brain. With over 700 living species of cone snails, each having up to...
HHMI's Holiday Lectures on Science
Mar 8, 2010 HHMI/E.O. Wilson & Eric Chivian
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Questions on biodiversity, endangered habitats, and how best to preserve the Earth's ecosystems, are answered by Dr. E.O. Wilson of the Department of Organismic and Evolutionary Biology at Harvard University, Dr. Eric Chivian of the Center for Health and the Global Environment at Harvard Medical School, Dr. Bassler and Dr. Olivera. Drs. Wilson and Chivian deliver short presentations on biodiversity to start the session. The question and answer session is moderated by HHMI President Dr. Robert...
HHMI's Holiday Lectures on Science
Apr 1, 2009 HHMI
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Dr. Kay Jamison of the Johns Hopkins University School of Medicine, and Dr. Gerald Fischbach of the Simons Foundation, join Drs. Kandel and Jessell to address student comments and questions concerning autism, manic depression, and other mental illnesses.
HHMI's Holiday Lectures on Science
Apr 1, 2009 HHMI/Thomas M. Jessell, PhD
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Behavior involves movement. Movement drives simple respiratory programs to keep us breathing, as well as displays of emotion—desire, joy, remorse—that project our inner thoughts and moods. Understanding the workings of the neural circuits that control movement gives us a glimpse of how brain wiring and circuit activity control specific behaviors, including one of the more sophisticated aspects of human motor behavior—the movement of our limbs. Consider baseball player Lou Gehrig's...
HHMI's Holiday Lectures on Science
Apr 1, 2009 HHMI/Eric R. Kandel, MD
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Do the brain's two major memory systems—implicit and explicit—have any common features? Can molecular biology, which has enhanced understanding of many other bodily functions, help us understand mental function? Implicit and explicit memory both have a short-term component lasting minutes (for example, remembering the telephone number you just looked up) and a long-term component that lasts days, weeks, or a lifetime (for example, remembering your mother's birthday). For both memory...
HHMI's Holiday Lectures on Science
Apr 1, 2009 HHMI/Eric R. Kandel, MD
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What is mind? A central finding is that mind is a series of processes carried out by the brain. Mind is to the brain as walking is to legs—but it is infinitely more complex. The brain produces our every emotional, intellectual, and athletic act. It allows us to acquire new facts and skills and to remember them for as long as a lifetime. Mind emerges from brain activity, and specific mental functions are localized to different regions in the brain. Over the past few decades, we have found that...
HHMI's Holiday Lectures on Science
Apr 1, 2009 HHMI/Thomas M. Jessell, PhD
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The human brain is the sophisticated product of 500 million years of vertebrate evolution, assembled during just nine months of embryonic development. The functions encoded by its trillion nerve cells direct all human behavior—from the simple movements of everyday life to the daring and inspirational thoughts that sometimes emerge. Yet the brain is a biological organ made from the same building blocks as skin, liver, and lung. How does the brain acquire its remarkable computational power?...
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI/Bisola O. Ojikutu, MD, MPH
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In 1981, an obscure and deadly disease surfaced. Previously healthy homosexual men in the United States began arriving at clinics with rare cancers and infections usually seen in people with weakened immune systems. Most of them died. The medical community was baffled and the public anxious. As the cases multiplied, so did the questions. Who is at risk? What is causing the disease? Why does it lead to failure of the immune system? And most important: Can it be stopped from spreading? The new...
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI
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A 90-minute discussion session with the lecturers, Washington, D.C.-area high school students, and three students—Piali Mukhopadhyay, Shefali Oza, and Stella Safo—who are helping in the global fight against HIV and AIDS.
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI/Bisola O. Ojikutu, MD, MPH
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In 1987, four years after HIV was identified, the Food and Drug Administration (FDA) approved the use of azidothymidine (AZT) to slow the progression of HIV infection to full-blown AIDS. AZT targets reverse transcriptase, an enzyme essential to HIV replication in lymphocytes. Unfortunately, HIV evolves rapidly and develops resistance to AZT, making single-drug therapy with reverse transcriptase inhibitors ineffective. In 1996, a new class of antiretroviral drugs, called protease inhibitors, was...
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI
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A 90-minute discussion session with the lecturers, Washington, D.C.-area high school students, and three HIV-positive individuals—Adam Barrett, Zinhle Thabethe, and Phill Wilson—who share their personal experiences about living with HIV.
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI/Bruce D. Walker, MD
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The global HIV epidemic continues to spread: 40 million people are infected worldwide. While drugs are essential in the battle against HIV, a vaccine would be a major advance. A vaccine, for example, can be preventive and does not require frequent dosing. HIV's ability to evolve rapidly is a major hurdle in developing a vaccine. HIV replication uses a reverse transcriptase enzyme that converts viral RNA into DNA. The enzyme is poor at reading and correcting mistakes. With successive replication...
HHMI's Holiday Lectures on Science
Apr 1, 2008 HHMI/Bruce D. Walker, MD
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The first AIDS cases—otherwise healthy young men with multiple infections and cancers—were a mystery to even the most seasoned physicians. The symptoms pointed to a major defect in the immune system. Further investigation found swollen lymph nodes, another sign of immune stress. A clear hypothesis emerged: the cells of the immune system were directly infected. Tissue cultured from patients' lymph nodes revealed a new virus—a retrovirus. This type of virus contains RNA that it converts to...
HHMI's Holiday Lectures on Science
Sep 4, 2007 HHMI/Michael Rosbash, PhD
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Dr. Rosbash discloses how scientists have persuaded Mother Nature to reveal the inner workings of the fruit fly's biological clock. From the almost 14,000 genes in this organism, scientists have painstakingly identified a handful that regulate the "ticktock" of the biological clock. In doing so, scientists have also brilliantly shown how the environment resets our biological clocks so that they are in synchrony with the cycles of nature.
HHMI's Holiday Lectures on Science
Sep 4, 2007 HHMI/Michael Rosbash, PhD
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Dr. Rosbash reveals that the fruit fly (Drosophila melanogaster) has a biological clock in its nervous system. Although tiny in size, the fruit fly has had a major impact on our understanding of circadian rhythms. The fruit fly served as the instrument with which scientists proved that certain behaviors such as rest and activity are under direct genetic control. Although much remains to be learned, the outlines of how the biological clock functions have emerged from research on this singular...
HHMI's Holiday Lectures on Science
Sep 4, 2007 HHMI/Joseph S. Takahashi, PhD
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After describing the fundamental properties of circadian rhythms, Dr. Takahashi takes us on an exciting journey into a very special region of the brain—the suprachiasmatic nucleus (SCN). The SCN functions as a "master" biological clock that governs our physiology and certain behaviors. The clock regulates rhythms of sleep and wakefulness that make us morning larks, evening owls, or something in between. When the master clock is out of synchrony with other biological clocks in the...
HHMI's Holiday Lectures on Science
Sep 4, 2007 HHMI/Joseph S. Takahashi, PhD
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Dr. Takahashi describes the powerful strategies that he and others have harnessed for understanding biological clocks in mammals. To tease out the secrets of how the clocks in higher organisms function, scientists had to overcome uncommonly high hurdles posed by the complexity of mice, hamsters, and humans. Many of these studies used the increasingly important research tools of genomics and computer-based informatics. One payoff already is a better understanding of human sleep disorders that...
HHMI's Holiday Lectures on Science
Aug 1, 2007 HHMI/Barbara J. Meyer, PhD
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Dr. Meyer explains the value of studying model organisms and introduces the nematode C. elegans Affectionally known as "the worm," it has two sexes: male, which possesses a single X chromosome, and hermaphrodite, which possesses two X chromosomes. Dr. Meyer explains that sex determination is controlled by the xol-1 gene. Xol-1 gene expression is regulated by sex-determining factors produced by the X chromosome.
HHMI's Holiday Lectures on Science
Aug 1, 2007 HHMI/David C. Page, MD
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Is it a boy or a girl? Dr. Page looks at how we define male and female and summarizes the development of human sex characteristics. He then explains the role of the sex chromosomes, X and Y, and, in particular, the SRY gene. Dr. Page demonstrates the differences between species that reproduce sexually and those that reproduce clonally without sex. A likely major advantage of sexual reproduction is that meiotic recombination and subsequent natural selection can weed out deleterious mutations.
HHMI's Holiday Lectures on Science
Aug 1, 2007 HHMI/Barbara J. Meyer, PhD
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Having too many chromosomes can lead to too much gene expression. If a male and a female have a different number of X chromosomes, a dosage-compensation mechanism is necessary to equalize the level of gene expression. In human females who have two X chromosomes, one X chromosome in each cell is inactive, while in C. elegans hermaphrodites, the activity of both X chromosomes is reduced by half. Dr. Meyer explains how the gene that controls dosage compensation in C. elegans works. Some genes...
HHMI's Holiday Lectures on Science
Aug 1, 2007 HHMI/David C. Page, MD
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Dr. Page interprets the results of an audience-participation experiment comparing testosterone levels in males and females of varying ages. He then explains how the Y chromosome is inherited from father to son in a near clonal fashion. He demonstrates that successive inversions and deletions during mammalian evolution have reduced the Y chromosome to its present form--small and sparsely populated with genes. In some men, a deletion in the Y chromosome can lead to infertility. Dr. Page describes...
HHMI's Holiday Lectures on Science
Jul 2, 2007 HHMI/Thomas R. Cech, PhD
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Discovery of RNA's catalytic activity led to unexpected spin-offs, including a new scenario for the origin of life. In a different area, the ability of RNA catalysts (ribozymes) to cut and splice RNA molecules has sparked efforts to develop them as pharmaceuticals against viruses, cancer, and genetic diseases.
HHMI's Holiday Lectures on Science
Jul 2, 2007 HHMI/Thomas R. Cech, PhD
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Life processes are fundamentally chemical reactions. Left to themselves, however, the reactions would occur too slowly and nonspecifically to sustain life. Cellular enzymes are catalysts that tame reactions by accelerating them, lending specificity, and regulating their time and place. Some principles of biological catalysis are demonstrated.
HHMI's Holiday Lectures on Science
Jul 2, 2007 HHMI/Thomas R. Cech, PhD
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RNA and protein are built from different chemical units and assembled in distinct ways. Thus, the ability of RNA to exhibit catalytic activity rivaling that of traditional protein enzymes was unexpected. Studies of RNA catalytic centers have revealed much about their structure and mode of action.
HHMI's Holiday Lectures on Science
Jul 2, 2007 HHMI/Thomas R. Cech, PhD
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Chromosomes of humans and other eukaryotes contain linear DNA molecules. The chromosome ends, or telomeres, are necessary for DNA stability and replication. Telomere replication is carried out by telomerase, whose RNA subunit acts as a template for telomeric DNA synthesis.
HHMI's Holiday Lectures on Science
Jun 4, 2007 HHMI/B. Brett Finlay, PhD
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With bacteria invading our best weapons, where do we begin to search for new weapons? Dr. Finlay showcases three types of bacteria--E. coli, Salmonella, and Listeria--to illustrate how molecular biology is allowing researchers to probe the molecular workings of bacterial infections. He describes how these pathogens use their genetic "toolkits" of virulence factors to cause disease. These factors, as diverse as the hosts they invade, can be transferred between different bacteria by...
HHMI's Holiday Lectures on Science
Jun 4, 2007 HHMI/B. Brett Finlay, PhD
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Dr. Brett Finlay explains why bacterial diseases continue to be a major health problem worldwide, causing a third of the world's deaths every year. After describing how bacteria grow, reproduce, and spread, Dr. Finlay explains how antibiotics work--and why they are not always successful in stopping infection. He describes the "genetic Internet" that enables certain pathogenic bacteria or "superbugs" to "download" genes that are resistant to all available...